Add missing PIPX_BIN_DIR

Author: raulcd

ci/docker/python-wheel-windows-vs2022-base.dockerfile

@@ -110,6 +110,7 @@ RUN curl https://dl.min.io/server/minio/release/windows-amd64/archive/minio.RELE
     --output "C:\Windows\Minio.exe"
 
 # Install the GCS testbench using a well-known Python version.
+ENV PIPX_BIN_DIR=C:\\Windows\\
 ENV PIPX_PYTHON_VERSION=3.11
 RUN pymanager install %PIPX_PYTHON_VERSION%
 COPY ci/scripts/install_gcs_testbench.bat C:/arrow/ci/scripts/